The rear end of a 126 body bears no resemblance to the 190 and newer rear suspensions. It also hardly ever has any problems other than maybe shocks. There are no mechanisms for alignment as there is never any wear.
I would look to the front end. I don't relate your description to any of the many things I know can go wrong. Give us another description. Is there sudden play in the steering? If so I can only imagine that you have a very loose steering link somewhere up front.
Bosch Master, ASE Master, L1
33 years MB technician